This invention is directed to a thermoplastic control bonding and debonding complex for releasably securing distinct elements together, and in particular to the use of an exothermic carrier for controlling the adhesive bonding and debonding properties of a thermoplastic resin.
In recent years, thermoplastic resins commonly referred to as "hot melt glues", have become widely used due to their inherent ability to effect a bond rapidly. However, the inherent properties of thermoplastic resins that render same effective as an adhesive have made the use of such thermoplastic resins cumbersome and has limited the application of same to only a minimum of industrial uses.
Specifically, thermoplastic resins can only be applied to the surfaces of elements to be bonded together when the glue is heated to a substantially liquid state wherein same is able to be flowed onto the respective surfaces of the elements to be secured together. In its substantially liquid state, the resin is sticky and wets the surfaces of the elements to be bonded. Once exposed to ambient conditions, the temperature of the thermoplastic resin drops causing same to become substantially structural and acts as an adhesive bonding agent to fuse the wetted elements together. The term "open time" is utilized to define the time from which the thermoplastic resin is in a substantially liquid state and is capable of wetting a surface to the time when the thermoplastic resin is no longer sufficiently in liquid state to wet a surface. Stated otherwise, "open time" represents the total time available to apply a thermoplastic resin and effect bonding thereby. Thus, one difficulty heretofore encountered, in using thermoplastic resins as adhesives, is the short open time (typically 10 to 15 seconds) of such adhesives when applied by methods known in the prior art since the short open time limits the time available to achieve bonding using such adhesives, hence limiting the area of bonding that can be effected thereby.
Heretofore, all conventional methods of applying thermoplastic resins required a dispenser for dispensing quantities of the resin in a heated form wherein same is in a substantially liquid state to the members to be bonded. For example, hot melt guns have in themselves become expensive, intricate dispensers in order to sufficiently deliver the hot melt glue in a heated form to members that are to be adhesively bonded. As noted above, even if the resin is applied to the elements to be bonded under optimum conditions, the short open time requires that the bonding operation be instantly effected. Moreover, since thermoplastic resins will not efficiently wet surfaces that are cold, since the resin skims over upon contact with the cold surfaces, in order to take maximum advantage of the bonding strength of the resin, either the elements to be bonded must be warmed to optimum temperatures, which are often 250.degree. to 350.degree. F, or alternatively, the ambient conditions in which the bonding operation is effected must be sufficiently high as to avoid skimming of the resin upon contact with the element to be bonded. Finally, once effectively bonded by such adhesives, no method of debonding the respectively secured elements has heretofore been provided. Accordingly, a thermoplastic control complex for releasably securably bonding distinct elements together is desired.